Technical Field
The present disclosure mainly relates to a terminal used in automobiles and a method of manufacturing a terminal.
Background
A wire harness used in automobiles or the like is a connecting structural body in which terminals and coated wires are joined together. Currently, there are efforts towards replacement of a copper alloy with an aluminum alloy for a core wire of coated wires used in wire harnesses. However, there is a problem that corrosion between dissimilar metals is likely to occur at a contact between aluminum (aluminum alloy) constituting a core wire and copper (copper alloy) constituting a terminal. As corrosion progresses, a crack or a poor contact will occur at a connecting portion between the core wire and the terminal. In this regard, for further practical use in the future, studies are underway for obtaining a terminal with less corrosion problem.
For example, in order to eliminate corrosion, a connecting structural body exists in which a crimping portion between a copper terminal and an electric wire core is in a sealed state (Japanese Patent No. 4326797). Also, there are terminals composed of an aluminum alloy, which is the same as a material of a core wire of an electric wire (Japanese Laid-Open Patent Publication Nos. S53-122790, H4-41646, H4-41648 and 2013-54824).
However, according to Japanese Patent No. 4326797, a cap forming process is separately required to provide a sealed condition at a crimping portion between a copper terminal and a core wire, and a filler for waterproofing is disposed between the cap and the core wire. Accordingly, a higher cost is required than conventional terminals. This results in a higher cost for the terminal and the core wire in total, even if cost reduction due to the replacement of a copper alloy with an aluminum alloy for the core wire is taken into account. This is one of the reasons why changing over to an aluminum alloy core wire is not spreading.
Japanese Laid-Open Patent Publication No. S53-122790 discloses using an aluminum alloy as a terminal material, but merely discloses an example using pure aluminum, and a strength and heat resistance thereof are not applicable for a terminal having a mating spring. According to Japanese Laid-Open Patent Publication Nos. H4-41646 and H4-41648, 6000-series aluminum alloys are used as terminal materials. However, since these are materials subjected to solution heat treatment and thereafter to an aging treatment at room temperature, it cannot be denied that they are poor in strength. According to Japanese Laid-Open Patent Publication No. 2013-54824, 2000-series, 6000-series, and 7000-series Al alloys are used as terminal materials, and a terminal is manufactured by casting, hot rolling, cold rolling and various heat treatment steps. However, there is a problem that they have a high strength and a poor formability during the forming and working, and thus there is a difficulty in processing a sheet material into a terminal.
The present disclosure is related to providing a terminal having a higher strength and improved stress relaxation resistance, and showing a low contact resistance as a terminal initially and after an endurance test. Further, the present disclosure is related to providing a manufacturing method for forming a terminal having an effect described above in an improved manner.